I actually saw this for the first time a week after watching the remake. This means, among other things, that any items I saw as borrowed from other films may, in fact, have originated with this one.
I did not see it when it came out because the reviews weren't that enticing, and, no doubt, there was something more interesting opening that week. Whatever I saw instead was, I am certain, a more satisfying movie, although this one not at all a bad one.
But enough of that. This is the sort of suspense story that plays with whether or not something supernatural is happening. It actually does a pretty good job of it, although I am not sure how realistic its view of medical school (I /think/ these guys are in medical school, as opposed to being residents, but I could be wrong) is.
And, of the two, this is the better movie. For one thing, I almost cared about the characters in this one (the characters in the remake could all have been eaten by the Bugblatter Beast for all I cared about them). I could also tell them apart but, of course, I have seen most of them in other films, which might not have been true had I seen it when it came out.